Salarias fasciatus — Lawnmower Blenny
- Best for: hobbyists with mature tanks and live rock.
- Size: up to 13–14 cm.
- Real diet: detritivore–algivore; biofilm + nori/spirulina.
- Compatibility: peaceful; avoid mixing with conspecifics.
- Difficulty: moderate; requires observation and plant-based supplementation.
Introduction
Salarias fasciatus is a hardy blenny that grazes biofilm, detritus and fine algae from rocks and glass. In young tanks it may struggle to find food; in mature, live-rock systems it becomes an excellent natural reef maintenance crew.
«When microalgae and biofilm are plentiful, this fish works around the clock; when they’re not, you need to support it with quality plant-based food.»
— AtlasReef ExperienceIdentification & Taxonomy
| Field | Data |
|---|---|
| Scientific name | Salarias fasciatus (Bloch, 1786) |
| Family | Blenniidae |
| Common names | Lawnmower blenny, Jeweled blenny, Sailfin blenny |
| Maximum size | ~13–14 cm |
| Distribution | Indo-Pacific: shallow reefs, lagoons and flats |
Habitat & Behaviour
Inhabits well-lit rocky reefs and rubble zones, perching to graze and survey its territory. It can be assertive toward similarly shaped species (other blennies/gobies) but typically ignores mid-water fish.
Recommended Tank Setups
Works best in systems with live rock and well-lit areas. In SPS/LPS reef tanks it leaves corals alone but may scrape biofilm from nearby surfaces.
Water Parameters
| Parameter | Practical range | Notes |
|---|---|---|
| Temperature | 24–27 °C | Avoid spikes; stability above all. |
| Salinity | 1.024–1.026 sg | Standard reef. |
| pH | 8.0–8.4 | Gentle daily swings are normal. |
| Nitrates | < 15 mg/L | Ideally 2–10 mg/L for biological stability. |
| Phosphates | < 0.1 mg/L | Some PO4 helps avoid «zero-nutrient» starvation. |
Feeding
Although called an «algae eater», evidence shows a mixed diet with a high proportion of detritus and microfauna alongside filamentous algae and diatoms. In a mature tank it can largely self-sustain, but supplementation is advised.
What worked / What didn’t — maintaining good condition
✅ Worked
- Offering nori clipped to the glass 1–2×/day.
- Pellets/flakes with spirulina and high plant content.
- Vegetable gel foods and blanched vegetables (zucchini/spinach) in small portions.
❌ Didn’t work
- Relying solely on bare rock in ultra-low-nutrient systems.
- Large infrequent feedings → waste and apathy.
Compatibility
Peaceful with most reef fish. Can be territorial toward other Salarias or similarly shaped blennies in small tanks. Coral-safe; may rest on colonies (Montipora/Porites) without harming them.
Comparison: S. fasciatus vs S. ramosus
Two very similar algivorous blennies often found in the trade. This table summarises practical differences to help you choose the right one for your tank.
| Feature | S. fasciatus | S. ramosus |
|---|---|---|
| Maximum size | 13–14 cm | ~10–11 cm |
| Coloration | Brown/green mottling; prominent cephalic cirri | More regular pale spotting |
| Natural diet | Detritivore–algivore (biofilm, filamentous algae, microfauna) | More algivore; relies on visible algae |
| Temperament | Territorial toward conspecifics/similar blennies | Slightly more tolerant |
| Best for | Mature systems with live rock and biofilm | Mid-size tanks seeking extra algae control |
| Difficulty | Moderate (needs plant supplement) | Low-moderate (if algae available) |
«If your tank is mature and you want a very active fish: fasciatus. If you’d prefer something smaller and more of a visual algae eater: ramosus.»
— AtlasReef ExperienceBCI — Body Condition Index
A quick guide to assess whether your Salarias is maintaining good condition. Use the belly line and flank fullness as your reference.
BCI 1 — Emaciated
Critical- Sunken belly, concave flanks.
- Erratic picking or lethargy.
Action: daily nori + vegetable gel food; reduce competition.
BCI 2 — Thin
Needs improvement- Straight or slightly concave ventral line.
- Active grazing but tires easily.
Action: add 1–2 small extra plant-based feedings per day.
BCI 3 — Good
Target- Flat or slightly convex belly.
- Constant picking, normal behaviour.
Action: maintain routine and stability.
BCI 4 — Overweight
Monitor- Very convex abdomen; visible fat.
- Reduced activity.
Action: reduce fatty pellets; prioritise plant fibre.
Myths vs Facts
| Myth | Fact | What to do |
|---|---|---|
| «It only eats algae.» | Mixed diet with substantial biofilm/detritus. | Offer nori/spirulina daily in small amounts. |
| «If there’s algae, that’s enough.» | Visible algae ≠ sufficient nutrition. | Monitor BCI and adjust supplementation. |
| «It nips corals.» | It perches; it does not typically bite polyps. | Provide perches and resting spots. |
Compatibility Matrix
| Group | Compatibility | Notes |
|---|---|---|
| Clownfish | High | Ignore the blenny. |
| Gobies/blennies | Medium | Similar shape → disputes. |
| Other Salarias | Low | Only in large tanks with ample refuges. |
| Herbivorous tangs | Medium | Compete for grazing; add extra nori. |
| SPS/LPS corals | High | Rests on them without causing damage. |
Express Buying Guide
✅ Signs of good health
- Flat or slightly convex belly (BCI ≥ 3).
- Constant picking at glass/rocks in the store tank.
- Clear eyes, intact fins, active response when approached.
- Accepts nori/spirulina pellets in a quick feeding test.
❌ When NOT to buy
- Sunken belly and concave flanks (BCI 1–2).
- Lethargic, resting on the bottom without grazing.
- Wounds on the chin or erosion around the mouth.
- Store tank «too clean» with no visible biofilm.
Weight-Loss Risk Estimator
Tick everything that applies to your tank and count the ✓s.
| # | Statement | Applies? |
|---|---|---|
| 1 | Tank volume < 150 L. | |
| 2 | Live rock < 8% of volume (less than 8 kg per 100 L). | |
| 3 | System age < 4 months. | |
| 4 | Herbivore competitors ≥ 2 (tangs, other blennies, etc.). | |
| 5 | Current vegetable supplementation 0 times/day. |
Interpret: 0–1 ✓ = Low · 2–3 ✓ = Medium · 4–5 ✓ = High
Quick Glossary
Biofilm
Thin layer of microorganisms and detritus coating rocks/glass; a key food source.
Diatoms
Early-stage microscopic brown algae; ideal for tank cycling and grazing.
Perches
Flat surfaces (e.g., Montipora plate/rock) where the blenny rests to survey its territory.
Breeding (overview)
Demersal, adhesive spawning in crevices or cavities; the male typically guards the eggs. Larvae are planktonic and drift before settling. Captive breeding has been reported occasionally; it requires refuges and live microalgae food after hatching.
Health
The most common issue is loss of body condition due to insufficient biofilm/algae. Opportunistic infections can also arise from abrasion wounds. Prevention: stable water, adequate diet and quarantine.
| Situation | Signs | What to do |
|---|---|---|
| Weight loss | Visible abdominal cavity | Increase plant-based food (nori/spirulina) and reduce competition. |
| Territorial stress | Chasing with other blennies | Rearrange rockwork and add refuges; consider separating individuals. |
| Abrasion wounds | Marks on chin/mouth | Improve water quality; watch for signs of infection. |
Common Mistakes
- Do not introduce into new tanks without established biofilm.
- Do not house with other Salarias in small tanks.
- Do not assume it «only eats algae»: it needs a varied, fibre-rich diet.
Scientific Evidence (2018–2025)
Diet and feeding morphology
- Natural diet including detritus, diatoms, microfauna and algae; comb-like dentition for substrate scraping. J. Fish Biology
- Taxonomic/ecological summary, size and distribution. FishBase
Reef ecology
- Role of detritivores in matter flow and reef resilience. Nature Communications
- Regional distribution and occurrence records. Fishes of Australia · PBIF SPREP datasets
Reproduction & captive breeding
- Captive spawning/larvae report (hobbyist breeders). Breeders Registry
Practical guides & technical profiles
- Aquarium profiles and husbandry: Saltcorner · ReefApp · ReefChasers
Further Reading
- Salarias ramosus — full species profile
- Marine aquascaping
- Bioindicators in reef tanks
- Tang fish guide
- Marine quarantine
- Hospital tank
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FAQ — Salarias fasciatus
Is it safe with corals?
Yes. It may perch on colonies without harming them; it scrapes biofilm from the base. It does not typically nip polyps actively.
Does it need a mature tank?
Highly recommended: live rock with established biofilm prevents loss of body condition. In young tanks with no biofilm it can starve quickly.
Will it accept prepared foods?
Many individuals accept nori, spirulina and vegetable pellets. Offer small frequent portions; large feedings are usually ignored.
Can I keep two together?
Only in large tanks with multiple hiding spots; they can fight over shape/territory. In smaller tanks one specimen is preferable.
Does it control all algae?
No. Results vary by individual and algae type; it is a helper, not a magic solution. It will not tackle tough filamentous algae or cyanobacteria.
«A well-observed reef is a well-kept reef.»
— AtlasReef · Salarias fasciatusImages: AtlasReef Media Library (original/AI, rights-free). · Guide written by AtlasReef.